Gary Robbins dreams of becoming just the 16th person ever to finish the Barkley Marathons got derailed after he made a wrong turn in Frozen Head State Park in Tennessee.

In a blog post on his website following the heartbreaking finish, Robbins laid out exactly what happened during what is considered by some to be the hardest race in the world.

"In the fog I was a few degrees off course and when I hit my trail I must've trended into it left and then continued following it," Robbins wrote in the April 4th post.

"One fatal error with just over two miles to go haunts me."

Gruelling race

The Barkley Marathons is a unique 160 kilometre race that sees competitors from all over the world come and try to tackle five long loops of the course. The 40 people who get accepted to enter each year only have 60 hours to compete all five laps.

Last year, Robbins was left hallucinating in his first attempt. In 2017, a wrong turn left him fighting to finish.

"I bushwhacked down the mountain at breakneck speed and I found myself at a large river," Robbins wrote.

"The river was maybe 15 feet wide and absolutely raging from all the rain we were experiencing. I took one step off the river bank and was already chest deep. I would never have made the decision to attempt to swim such waters under anything other than a highly sleep deprived and stressed state of mind."

Rushing to beat the clock, Robbins started on the road to camp with just moments before the 60 hour mark.

"[I] put my head down and gutted out the hardest three minutes of my life to collapse at the gate, overtime, and from the wrong direction," he wrote.

Robbins collapsed at the finish. His time was 60 hours and six seconds.

However, the Mount Pearl, N.L.-born runner, who now calls Vancouver home, admits even if he was under the 60 hour limit, he shouldn't have been considered a Berkley Marathons finisher.

"My finish, even if it were six seconds faster would not have counted," Robbins wrote

"I put Laz [creator of the Barkley Marathons] and the race in a precarious situation and in hindsight I'm glad I was six seconds over so that we didn't have to discuss the validity of my finish."

Robbins offers up congratulations to the races 15th finisher, John Kelly, before thanking his family and crew team for their support.